Blocks of a conventional tread pattern are defined by circumferential major grooves extending in a tire circumferential direction and lug grooves extending in a tire width direction. Such a block pattern is excellent in driving and braking performance. Moreover, a sporty exterior image thereof has become popular in patterns for high performance cars. This pattern is used in snow tires, RV tires, and construction vehicle tires for use in snow and mud (for example, see Japanese Patent Laid-open publication No. 2002-362114).
To improve the performance on snow and ice of such tires, a method of increasing an edge effect by increasing the number of blocks or adding sipes is effective.
Depth of the sipes added to the blocks is usually not more than 60% of depth of the circumferential major grooves.
However, if the edge effect is simply increased, rigidity of the blocks decreases, and the blocks are more deformed, not resulting in an improvement in the performance on snow and ice. Moreover, the durability of the blocks and uneven wear are adversely affected.
In the light of the aforementioned problem, an object of the present invention is to provide a pneumatic tire with performance on snow and ice and wet performance improved by increasing the edge effect while maintaining block rigidity.